Hello:
In an effort to sort out some of the terminology we are dealing with in regards to "Hardened Platforms", AttachPoints, Effect Triggers, and Custom Textured Ground Polygons, here's some info from the much more readable ESP version of the FSX SDK documentation:
http://msdn.microsoft.com/en-us/library/cc526976.aspx
"The Attach Tool
The Attach tool included in this SDK is a MAXScript plugin that allows you to attach special effects, library objects, visibility conditions, and set active mouse rectangles for use with virtual cockpits, to your 3D models. It also allows you to create landable platforms, remove crash boxes from parts of your model and attach beacons or other simulation driven objects to your models.
Platform
A platform is a piece of geometry that an aircraft can land on. By default all objects have crash boxes associated with them. Designating an object as a platform will make it landable as well as remove crash boxes from an area around that object (based on the crash box size used in XtoMDL). Use the drop-down list to determine the surface type of the platform (for example: Concrete, Grass, Tarmac, etc.)
Platforms are also used for bridges created as scenery objects (that is, not for extrusion bridges, which are explained in Compiling BGL). A road bridge over water, for example, should have a platform that matches the route of the cars over the bridge, otherwise the cars will drop and cross the water.
No Crash
Removing crash boxes from geometry allows you to create portions of your model that the aircraft will not crash into. This is especially handy when working with platforms. It is important to separate the geometry that does not require crash boxes from the rest of the model."
FYI: Other important CAVEATS to keep in mind:
"There is a limit to the amount of polygons a platform can have. I forgot the exact number, but it is relatively low. Making a platform of a whole island won't work and it would also kill your performance"
http://www.fsdeveloper.com/forum/showpost.php?p=129842&postcount=19\
"If you have two platforms within sight, and aircraft shadows enabled, FS9 will crash - aircraft shadows do not work with several landable surfaces. The projection of the shadows is nonsense anyways."
http://www.fsdeveloper.com/forum/showthread.php?t=1535&highlight=platform+crash
http://www.fsdeveloper.com/forum/showthread.php?t=39520&highlight=platform+crash
"If you hit a platform too hard, you will fall through it"
http://forum.fsdeveloper.com/forum/showpost.php?p=39822&postcount=3
"Users may also experience fall-through issues if"
- Their FS slider-settings are set too high for your PC's current capabilities.
- They descend too fast onto the platform.
The former is often a problem as the majority of fsx users probably have overly elevated slider settings.
A work-around to minimize fall-throughs is to create 2 additional hardens positioned say 5mm & 10mm respectively below the primary-surface harden."
http://www.fsdeveloper.com/forum/showpost.php?p=192367&postcount=2
IIUC, this is why at an ex: airport made using "hardened platforms", the reason aircraft are not still "falling through" the custom textured sloping RWY made using "hardened platforms" is that what one is actually landing on is the underlying FS terrain mesh and/or 'flat' or 'sloped' flatten... as THE definitive and truly hard "ground" entity (and AFAIK for which a "Crash" attribute cannot be excluded).
IMHO, those making flat / planar custom textured ground polygons at airports etc. to achieve display of higher resolution aerial imagery on top of their terrain than is otherwise achievable with mesh-clinging custom photoreal land class textures via ex: FSX SDK Resample directly or via SBuilderX, FS Earth Tiles (aka "FSET")... must consider the potential workload on the FSX rendering engine imposed by:
* The higher resolution density of pixels / texels and LOD associated MIPs in the mapped texture
* Any locally involved transparency to achieve texture blending etc. (transparency is computationally expensive)
* The 3D ground polygon object itself (even if 'flat') and any LOD associated MIPs in the model
* The Attached "hardened platform" Effect (and/or "2" more Attached "hardened platform" Effects to prevent 'fall-through' as stated above: Total="3" !
)
Al these factors will, by virtue of being computationally more complex, ultimately produce an impact on FPS; this impact may possibly be imperceptible, or may produce "stuttering" when the "hardened platform" scenery area is in view.
So, IMO, one must be certain of the necessity for using "hardened platforms" for a flat RWY that likely already has a flatten beneath the traditionally flat airport background where one intends to use AI traffic, because having already placed such an airport background flatten there may effectively make adding a "hardened platform" an unnecessary redundancy, and at the worst... a FPS-killer.
FYI: "a FSX runway (unlike FS9) has a built in flatten that uses a bounding box"
http://www.simforums.com/forums/topic22204_post126030.html#126030
A sloping RWY can be:
...Or a sloping RWY can be:
PS: For more info on airport design with control over RWY, Apron, and Taxiway surfaces (whether terrain is flat or not...) and/or aircraft ground roll effects see:
http://www.fsdeveloper.com/forum/showpost.php?p=234725&postcount=5
...and:
http://www.fsdeveloper.com/forum/showthread.php?t=18345&highlight=SCASM+runway+effect
I hope this serves to stimulate some further discussion < even if in a spirit of "friendly controversy"
> to help more thoroughly elaborate the factors at play when developing airports... with or without custom land class textures, custom textured ground polys, sloped flattens, or "hardened platforms". 
GaryGB
In an effort to sort out some of the terminology we are dealing with in regards to "Hardened Platforms", AttachPoints, Effect Triggers, and Custom Textured Ground Polygons, here's some info from the much more readable ESP version of the FSX SDK documentation:
http://msdn.microsoft.com/en-us/library/cc526976.aspx
"The Attach Tool
The Attach tool included in this SDK is a MAXScript plugin that allows you to attach special effects, library objects, visibility conditions, and set active mouse rectangles for use with virtual cockpits, to your 3D models. It also allows you to create landable platforms, remove crash boxes from parts of your model and attach beacons or other simulation driven objects to your models.
Platform
A platform is a piece of geometry that an aircraft can land on. By default all objects have crash boxes associated with them. Designating an object as a platform will make it landable as well as remove crash boxes from an area around that object (based on the crash box size used in XtoMDL). Use the drop-down list to determine the surface type of the platform (for example: Concrete, Grass, Tarmac, etc.)
Platforms are also used for bridges created as scenery objects (that is, not for extrusion bridges, which are explained in Compiling BGL). A road bridge over water, for example, should have a platform that matches the route of the cars over the bridge, otherwise the cars will drop and cross the water.
No Crash
Removing crash boxes from geometry allows you to create portions of your model that the aircraft will not crash into. This is especially handy when working with platforms. It is important to separate the geometry that does not require crash boxes from the rest of the model."
FYI: Other important CAVEATS to keep in mind:
"There is a limit to the amount of polygons a platform can have. I forgot the exact number, but it is relatively low. Making a platform of a whole island won't work and it would also kill your performance"
http://www.fsdeveloper.com/forum/showpost.php?p=129842&postcount=19\
"If you have two platforms within sight, and aircraft shadows enabled, FS9 will crash - aircraft shadows do not work with several landable surfaces. The projection of the shadows is nonsense anyways."
http://www.fsdeveloper.com/forum/showthread.php?t=1535&highlight=platform+crash
About eight years ago I made a very smooth arched overpass "taxiway" that bridged across a four-lane, divided highway to reach the airport's relief runway on the opposite side.
Too bad that AI couldn't use it though...
http://www.fsdeveloper.com/forum/showthread.php?t=39520&highlight=platform+crash
"If you hit a platform too hard, you will fall through it"
http://forum.fsdeveloper.com/forum/showpost.php?p=39822&postcount=3
"Users may also experience fall-through issues if"
- Their FS slider-settings are set too high for your PC's current capabilities.
- They descend too fast onto the platform.
The former is often a problem as the majority of fsx users probably have overly elevated slider settings.
A work-around to minimize fall-throughs is to create 2 additional hardens positioned say 5mm & 10mm respectively below the primary-surface harden."
http://www.fsdeveloper.com/forum/showpost.php?p=192367&postcount=2
IIUC, this is why at an ex: airport made using "hardened platforms", the reason aircraft are not still "falling through" the custom textured sloping RWY made using "hardened platforms" is that what one is actually landing on is the underlying FS terrain mesh and/or 'flat' or 'sloped' flatten... as THE definitive and truly hard "ground" entity (and AFAIK for which a "Crash" attribute cannot be excluded).
IMHO, those making flat / planar custom textured ground polygons at airports etc. to achieve display of higher resolution aerial imagery on top of their terrain than is otherwise achievable with mesh-clinging custom photoreal land class textures via ex: FSX SDK Resample directly or via SBuilderX, FS Earth Tiles (aka "FSET")... must consider the potential workload on the FSX rendering engine imposed by:
* The higher resolution density of pixels / texels and LOD associated MIPs in the mapped texture
* Any locally involved transparency to achieve texture blending etc. (transparency is computationally expensive)
* The 3D ground polygon object itself (even if 'flat') and any LOD associated MIPs in the model
* The Attached "hardened platform" Effect (and/or "2" more Attached "hardened platform" Effects to prevent 'fall-through' as stated above: Total="3" !
)Al these factors will, by virtue of being computationally more complex, ultimately produce an impact on FPS; this impact may possibly be imperceptible, or may produce "stuttering" when the "hardened platform" scenery area is in view.
So, IMO, one must be certain of the necessity for using "hardened platforms" for a flat RWY that likely already has a flatten beneath the traditionally flat airport background where one intends to use AI traffic, because having already placed such an airport background flatten there may effectively make adding a "hardened platform" an unnecessary redundancy, and at the worst... a FPS-killer.
FYI: "a FSX runway (unlike FS9) has a built in flatten that uses a bounding box"
http://www.simforums.com/forums/topic22204_post126030.html#126030
A sloping RWY can be:
- A series of flat ground polygons positioned to create a terrain "shape", each polygon being individually textured with either a default or custom terrain texture image "bitmap".
- Made as a "hardened platform" surface to prevent aircraft from "falling through" (...but unless a total of "3" such platforms are used, this works only if the aircraft makes a VERY "soft landing").
- Made with all 3D ground polygon surfaces precisely aligned so that their top surfaces closely match that of the terrain mesh (...which would be difficult if not impossible to achieve on end users FS installations / configurations without some "Z-Buffer fighting" artifacts being visible at various aircraft altitudes when flying around the aerodrome).
...Or a sloping RWY can be:
- A Triangulated Irregular Network (aka "TIN") ...the vertices for which are outside of a "concave" polygon which is built at a distance outside ones central airport flatten.
- Applied as a legacy LWM3 'tilted' flatten or newer CVX vector 'sloped' flatten surface (which locally over-rides and modifies the shape of the underlying FS terrain mesh)
- Textured with a mesh-clinging default or custom terrain texture polygon (AFAIK, actually a land class "texture" which must already be defined in Terrain.Cfg).
PS: For more info on airport design with control over RWY, Apron, and Taxiway surfaces (whether terrain is flat or not...) and/or aircraft ground roll effects see:
http://www.fsdeveloper.com/forum/showpost.php?p=234725&postcount=5
...and:
http://www.fsdeveloper.com/forum/showthread.php?t=18345&highlight=SCASM+runway+effect
I hope this serves to stimulate some further discussion < even if in a spirit of "friendly controversy"
> to help more thoroughly elaborate the factors at play when developing airports... with or without custom land class textures, custom textured ground polys, sloped flattens, or "hardened platforms". GaryGB
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